Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2012	Feb. 20, 2013	Jun. 30, 2012
Document and Entity Information [Abstract]
Entity Registrant Name	NATIONAL BANKSHARES INC
Entity Central Index Key	0000796534
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 200,195,893
Entity Common Stock, Shares Outstanding		6,947,974
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	true
Amendment Description	National Bankshares, Inc. (the “Company”) is filing this Amendment No. 1 to the Annual Report on Form 10-K (“Form 10-K/A”) filed as of and for the year ended December 31, 2012 (the “Form 10-K”) with the Securities and Exchange Commission to revise certain disclosures in Items 7, 8, 9A and 15. This Amendment does not reflect events that have occurred after the filing of the initial Form 10-K, and does not modify or update the disclosure therein in any way other than as required to reflect the matters set forth herein. Pursuant to Rule 12b-15 of the Securities Exchange Act of 1934, currently dated certifications from our principal executive and principal financial officers are filed, as required by Section 302 of the Sarbanes-Oxley Act of 2002.
Document Period End Date	Dec. 31, 2012